NEWTOWN, Conn. — Inside the four-bedroom colonial set on a small rise, Nancy Lanza was already dead. But it was early yet, and it would be hours before her body was found — time enough for her son to unleash a slaughter.

For now, though, all seemed idyllic in this 300-year-old town under crystalline skies.

Adam Lanza, 20 years old, fascinated by computers and recalled by former classmates as painfully awkward, left the house in his mother's car and drove past fine old churches and towering trees. It was the holiday season, and lawns were decorated with lights and electric reindeer. It was just five miles from home to Sandy Hook Elementary, where hallways and classrooms rang with talk of Hannukah and Christmas.

Inside the music room, a group of fourth-graders was watching the movie "The Nutcracker." Theodore Varga and some other teachers were meeting. Their students, the oldest kids in the school, were in specialty classes like gym and music. The glow remained from the previous night's fourth-grade concert.

"It was a lovely day," Varga said. "Everybody was joyful and cheerful. We were ending the week on a high note." The school appeared secure, it's entrance monitored by closed-circuit camera and opened only when employees in the main office buzzed somebody in. But Lanza wasted no time, breaking through the window and opening the door.

Someone turned the loudspeaker on, so everyone in the building could hear what was happening in the office.

"You could hear the hysteria that was going on," Varga said. "Whoever did that saved a lot of people. Everyone in the school was listening to the terror that was transpiring." The sounds reached a room where Principal Dawn Hochsprung and school therapist Diane Day along with a school psychologist, other staff members and a parent were gathered for a 9:30 meeting.

"We were there for about five minutes chatting, and we heard 'Pop! Pop!, Pop!'" Day told The Wall Street Journal. "I went under the table." A custodian ran around, warning people there was a gunman, Varga said.

"He said, 'Guys! Get down! Hide!'" Varga said.

Did he survive? The teacher did not know.

In the school, Hochsprung and school psychologist Mary Sherlach leaped out of their seats and ran out of the room. Hochsprung viewed her school as a model, telling The Newtown Bee newspaper in 2010 that "I don't think you could find a more positive place to bring students to every day." She had worked to make Sandy Hook a place of safety, too, and in October, the 47-year-old principal shared a picture of the school's evacuation drill with the message "Safety first." On this morning, Hochsprung didn't think twice about confronting the gunman. She died attempting to overtake him.

Sherlach also rushed to defend her students.

"Mary felt like she was doing God's work, working with children," her son-in-law Eric Schwartz told the South Jersey Times. She, too, was killed.

In a classroom, teacher Kaitlin Roig heard the shots and barricaded her 15 students into a tiny bathroom, sitting one of them on top of the toilet. She pulled a bookshelf across the door and locked it. She told the kids to be "absolutely quiet." "I said, 'There are bad guys out there now. We need to wait for the good guys,'" she told ABC News.

"The kids were being so good," she said. "They asked, 'Can we go see if anyone is out there?' 'I just want Christmas. I don't want to die. I just want to have Christmas.' I said, 'You're going to have Christmas and Hanukkah.'" One student claimed to know karate. "It's OK. I'll lead the way out," the student said.

"The shooting appears to have stopped," the dispatcher radioed at 9:38 a.m., according to the Post. "There is silence at this time. The school is in lockdown." And at 9:46 a.m., an anguished voice from the school: "I've got bodies here. Need ambulances."

Carefully, police searched room to room, removing children and staff from harm's way. They found Adam Lanza, dead by his own hand after shooting up two classrooms. No officer fired a gun.

All of the people killed at Sandy Hook Elementary School died from multiple wounds from a long gun and are classified as homicide victims, the state's chief medical examiner said Saturday.